Fission generators, however, are not devoid of drawbacks or danger. Being a nuclear process, fission produces radioactive waste which is difficult to dispose of properly. Although it takes less energy to split two atoms with fission than it does to fuse two atoms, the process is less stable and less efficient at harnessing useable energy. Furthermore, there is an increased risk of overloading a generator and causing it to explode if they are improperly maintained or used for extended periods of time. This, combined with growing fears of radiation poisoning and environmental contamination, has led watch-dog groups to lobby extensively against their use on many worlds throughout the galaxy.